Sterilization connotes the absence of all life forms, including bacterial endospores that are the living organisms most resistant to conventional sterilants. Disinfection, by distinction, only connotes the absence of pathogenic life forms (i.e., a bacterial endospore is not itself a pathogenic life form, but can produce such pathogens). Microbial decontamination is generic to both sterilization and disinfection.
Robust medical equipment is often sterilized at high temperatures. Commonly, the equipment is sterilized in a steam autoclave under a combination of high temperature and pressure. While such sterilization methods are very effective for more durable medical instruments, advanced medical instruments formed of rubber and plastic components with adhesives are delicate and wholly unsuited to the high temperatures and pressures associated with a conventional steam autoclave. Steam autoclaves have also been modified to operate under low pressure cycling programs to increase the rate of steam penetration into the medical devices or associated packages of medical devices undergoing sterilization. Steam sterilization using gravity, high pressure or pre-vacuum create an environment where rapid changes in temperature can take place. In particular, highly complex instruments which are often formed and assembled with very precise dimensions, close assembly tolerances, and sensitive optical components, such as endoscopes, may be destroyed or have their useful lives severely curtailed by harsh sterilization methods employing high temperatures and high or low pressures.
Further, endoscopes in particular present problems in that such devices typically have numerous exterior crevices and interior lumens which can harbor microbes and thus be difficult to clean and sterilize using ordinary techniques. The employment of a fast-acting yet gentle sterilization method is desirable for reprocessing sensitive instruments such as endoscopes. Other medical or dental instruments which comprise lumens are also in need of methods of cleaning and sterilizing which employ an effective reprocessing system which will not harm sensitive components and materials. Further, the need exists for a reprocessing system having a shorter reprocessing cycle time.
Early efforts to sterilize sensitive medical instruments, such as endoscopes, have met with limited success, and all conventional methods have associated problems or detractions. Sensitive medical instruments, such as endoscopes, are often sterilized by exposure to ethylene oxide which is thermally less severe than steam. The endoscope must be exposed to ethylene oxide-containing gas for a relatively long period, on the order of three to four hours. Thereafter, eight to twelve hours are normally required for de-gassing or desorbing ethylene oxide from plastic and other materials which are capable of absorbing the ethylene oxide. The pressurization and depressurization cycles of ethylene oxide sterilization may damage lens systems and other delicate instruments which are commonly integral with endoscopes. Moreover, the ethylene oxide is relatively expensive. It is sufficiently toxic and volatile that extensive precautions are commonly taken to assure operator safety. Other possible gaseous chemical sterilants include methyl bromide gas, beta-propiolactone gas, and ozone gas.
Liquid systems are commonly used for disinfecting endoscopes and other heat sensitive and delicate instruments. Use of liquid sterilants or disinfectants to achieve disinfection is normally rapid, cost-effective and does minimal damage to the medical devices. Current liquid chemical sterilants include glutaraldehyde solution, ortho-phthalaldehyde solution, formaldehyde solution, hydrogen peroxide solution, hydrogen peroxide/peracetic acid solution, and peracetic acid solution.
Commonly, a technician mixes a sterilant composition and manually immerses the item to be disinfected. Alternatively, a premixed sterilant composition can be used into which the item to be disinfected can be immersed. The immersion is timed by the technician. Technician variation in the mixing, timing and equipment handling raises problems of assurance and reproducibility of the manual disinfection process. Rinsing of the items to remove chemical residues also adds a variable that reduces the assurance of disinfection or sterility. Once rinsed, the disinfected endoscope or other item is susceptible to recontamination by airborne microbes.
Conventional liquid systems require complete immersion of the endoscope in the liquid solution. Large and bulky items such as endoscopes require large immersion containers and equally large volumes of expensive sterilant or disinfecting solution. Further, merely soaking endoscopes in a sterilant or disinfectant is less preferred since numerous pockets exist within the tubing that the sterilant or detergent cannot reach effectively. This leaves areas of potential contamination within the endoscope.
With the prevalence of highly contagious diseases such as Hepatitis B and Acquired Immune Deficiency Syndrome, effective sterilization, or disposal, of all medical tools becomes mandatory. Accordingly, an ineffective effort to sterilize endoscopes by merely soaking is unacceptable. For example, U.S. Pat. No. 5,091,343 discloses a liquid sterilization system which involves placing the instrument to be sterilized in a tray or cassette which is then covered and positioned within a liquid sterilization unit. Within the unit the cassette or tray is filled with liquid sterilant, rinsed with a sterile rinse water and the rinse water drained away. As the rinse water is drained away, sterile air is introduced into the cassette or tray. The cassette or tray is removed from the unit and the process is completed with uncovering the instrument and removing it for storage or use. A major drawback of this type of process is the lack of assurance of a sufficient flow of sterilant and rinse water through the interior passages of the instrument. The low pressure circulation of the liquid sterilant in the cassette or tray and the numerous pockets inherent in such a tubular instrument provides no assurance that adequate sterilization is attained in the interior passages of the instrument. The exterior surfaces of instruments, such as endoscopes, typically have multiple connectors and branches which can define small crevices or niches harboring microbes. Because of this, low pressure circulation liquid sterilization systems, which rely on complete submersion of the endoscope, may also be inadequate to assure complete sterilization of all exterior surfaces.
An improved approach is reported in U.S. Pat. No. 6,068,815 to Oberleitner, et al. Oberleitner reports a reprocessing system by which chemical sterilant is introduced to a lumen of an endoscope by pneumatic force.
Steam sterilization is widely considered to be the best available sterilization technique. A need exists to provide a device which can be used in combination with a fast-acting sterilization method to effectively reprocess and sterilize complex medical instruments having channels or lumens, in particular, such as endoscopes. Preferably, the device would be capable of combining all necessary reprocessing steps into a single system that can carry out the reprocessing of a device without or with reduced human intervention and without or with reduced harm to the medical device.